The present patent application relates to novel polymers, to the inverse water-in-oil microlatices comprising them and to their process of preparation. On the occasion of research directed at the development of novel inverse latices having prolonged stability over time, the Applicant Company had directed its efforts at the synthesis of polymers which result in water-in-oil microemulsions which, in comparison with conventional emulsions, are characterized by high thermodynamic stability. It has thus synthesized novel polymers which are appropriate for emulsions of this type.
According to a first aspect of the present invention, a subject-matter of the invention is a linear, branched or crosslinked polymer, characterized in that it is capable of being obtained by polymerization of N-alkylacrylamide with one or more monomers chosen from cationic monomers, monomers comprising at least one partially salified or completely salified strong acid functional group or monomers comprising at least one partially salified or completely salified weak acid functional group.
The alkyl radical substituting the acrylamide is linear or branched and comprises from one to six carbon atoms. According to a specific aspect of the present invention, the alkyl radical substituting the acrylamide is branched and is more particularly the isopropyl radical.
The term xe2x80x9cbranched polymerxe2x80x9d is understood to denote a nonlinear polymer which has pendant chains, so as to obtain, when it is dissolved in water, a high state of entanglement which results in very high viscosities at a low gradient.
The term xe2x80x9ccrosslinked polymerxe2x80x9d is understood to denote a nonlinear polymer which is provided in the form of a three-dimensional network which is insoluble in water but swellable in water and which results in a chemical gel being obtained.
The polymer according to the invention can comprise either crosslinked units or else branched units or else branched units and crosslinked units.
The strong acid functional group of the monomer comprising it is in particular the partially salified or completely salified sulphonic acid functional group or phosphonic acid functional group. The said monomer is, for example, partially salified or completely salified styrenesulphonic acid or partially salified or completely salified 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulphonic acid.
The weak acid functional group of the monomer comprising it is in particular the partially salified or completely salified carboxylic acid functional group, such as, for example, partially salified or completely salified 3-methyl-3-[(1-oxo-2-propenyl)amino]butanoic acid.
The cationic monomer is chosen particularly from quaternary ammonium derivatives. Examples of cationic monomers are the 2,N,N,N-tetramethyl-2-[(1-oxo-2-propenyl)amino]propanammonium, 2,N,N-tri-methyl-2-[(1-oxo-2-propenyl)amino]propanammonium or N,N,N-trimethyl-3-[(1-oxo-2-propenyl)amino]propanammonium salts.
The term xe2x80x9csalifiedxe2x80x9d is understood to denote, for the strong or weak acid functional groups, the alkali metal salts, such as the sodium salt or the potassium salt, or the nitrogenous base salts, such as, for example, the ammonium salt or the monoethanolamine salt (HOxe2x80x94CH2xe2x80x94CH2xe2x80x94NH3+).
A particular subject-matter of the invention is a polymer as defined above capable of being obtained by polymerization of an N-alkylacrylamide with one or more monomers having a 1-oxo-2-propenyl radical and more particularly a polymer capable of being obtained by polymerization of N-isopropylacrylamide with one or more monomers chosen from 2,N,N,N-tetramethyl-2-[(1-oxo-2-propenyl)amino]propanammonium halides, 2,N,N-trimethyl-2-[(1-oxo-2-propenyl)amino]propanammonium halides or N,N,N-trimethyl-3-[(1-oxo-2-propenyl)amino]propanammonium halides, partially or completely salified 3-methyl-3-[(1-oxo-2-propenyl)amino]butanoic acid or partially or completely salified 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulphonic acid.
Examples of such polymers are those capable of being obtained by copolymerization of N-isopropylacrylamide with sodium 3-methyl-3-[(1-oxo-2-propenyl)amino]butanoate or with sodium 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulphonate and those capable of being obtained by terpolymerization of N-isopropylacrylamide with a monomer chosen from sodium 3-methyl-3-[(1-oxo-2-propenyl)amino]butanoate or sodium 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulphonate and a monomer chosen from 2,N,N,N-tetramethyl-2-[(1-oxo-2-propenyl)amino]propanammonium chloride, 2,N,N-trimethyl-2-[(1-oxo-2-propenyl)amino]propanammonium chloride or N,N,N-trimethyl-3-[(1-oxo-2-propenyl)amino]propanammonium chloride.
According to a second aspect of the present invention, a subject-matter of the invention is a process for the preparation of a polymer as defined above, characterized in that:
a) an aqueous solution comprising the monomers and the optional additives, such as a crosslinking and/or branching agent, is emulsified in an oily phase in the presence of one or more surface-active agents, so as to form a microemulsion,
b) the polymerization reaction is initiated and then the said reaction is allowed to take place in order to form an inverse microlatex, and then
c) the said polymer is isolated.
The surface-active agent or the mixture of surface-active agents employed generally has an HLB number of greater than or equal to 9. The amount used is between approximately 5% by weight and approximately 10% by weight of the microemulsion.
A more particular subject-matter of the invention is a process as described above in which the mixture of surfactants employed comprises a mixture of at least one emulsifying agent of the water-in-oil type with at least one emulsifying agent of the oil-in-water type.
The term xe2x80x9cemulsifying agent of the water-in-oil typexe2x80x9d is understood to denote emulsifying agents having an HLB value which is sufficiently low to provide water-in-oil emulsions, such as sorbitan esters, for example sorbitan monooleate, sold by Seppic under the name Montane(trademark) 80, sorbitan isostearate, sold by Seppic under the name Montane(trademark) 70, or sorbitan sesquioleate, sold by Seppic under the name Montane(trademark) 83.
The term xe2x80x9cemulsifying agent of the oil-in-water typexe2x80x9d is understood to denote emulsifying agents having an HLB value which is sufficiently high to provide oil-in-water emulsions, such as ethoxylated sorbitan esters, for example sorbitan oleate ethoxylated with 20 mol of ethylene oxide, sold by Seppic under the name of Montanox(trademark) 80, decaethoxylated oleocetyl alcohol, sold by Seppic under the name of Simulsol(trademark) OC 710, or polyethoxylated sorbitan hexaoleates, sold by Atlas Chemical Industries under the names G-1086 and G-1096.
The oily phase of the microemulsion is composed either of a commercial mineral oil comprising saturated hydrocarbons, such as paraffins, isoparaffins or cycloparaffins, which exhibits, at ambient temperature, a relative density of between 0.7 and 0.9 and a boiling point of greater than 180xc2x0 C., such as, for example, Isopar(trademark), Exxsol(trademark) D 100 S or Marcol(trademark) 52, sold by Exxon Chemical, isohexadecane or isododecane, or a mixture of several of these oils.
Isohexadecane, which is identified in Chemical Abstracts by the number RN=93685-80-4, is a mixture of C12, C16 and C20 isoparaffins comprising at least 97% of C16 isoparaffins, among which the main constituent is 2,2,4,4,6,8,8-heptamethylnonane (RN=4390-04-9). It is sold in France by Bayer. Marcol(trademark) 52 is a commercial oil corresponding to the definition of liquid petrolatums the French Pharmacopoeia. It is a white mineral oil in accordance with the FDA 21 CFR 172.878 and CFR 178.3620 (a) regulations and it is included in the Pharmacopoeia of the USA, US XXIII (1995), and in the European Pharmacopoeia (1993).
If appropriate, the crosslinking and/or branching agent employed in the process as defined above is a diethylene or polyethylene compound in the molar proportion, expressed with respect to the monomers employed, of 0.005% to 1% and preferably from 0.01% to 0.2% and more particularly of 0.01% to 0.1%. It is, for example, ethylene glycol dimethacrylate, sodium diallyloxyacetate, ethylene glycol diacrylate, diallylurea, trimethylolpropane triacrylate or methylenebis(acrylamide).
The aqueous phase employed in stage a) of the process described above can comprise up to 50% of its weight of monomer.
The microlatex obtained on conclusion of stage b) comprises between approximately 20% and 50% by weight of water.
The process as described above can be employed batchwise, semi-continuously or continuously.
According to the final aspect of the present invention, the subject-matter of the invention is an inverse microlatex capable of being obtained by the implementation of stages a) and b) of the process as defined above.